Multiple shell grab



Jan. 6, 1959 H. ZIMMERMANN MULTIPLE SHELL GRAB 4 Sheets-Sheet 1 FiledJune 11, 1956 I r t m INVENTOR. Hark/*2 Z z'mmel'malzlz,

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Jan. 6, 1959 H. ZIMMERMANN MULTIPLE SHELL GRAB 4 Sheets-Sheet 4 FiledJune 11, 1956 INVENTOR. Herbal Zz'zrzmezwmzzz; BY

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United States Patent O MULTIPLE SHELL GRAB Herbert Zimmermann, Dortmund,Germany, assignor to Hoesch Werke Aktiengesellsclraft, Dortmund, WestGermany Application June 11, 1956, Serial No. 590,606

Claims priority, application West Germany December 19, 1955 15 Claims.(Cl. 37-182) This invention relates to a grab and more particularly to agrab of the multiple shell type which is adapted to be extended from theboom of a crane for lifting various objects and substances includingearth, stones and the like.

For many years multiple shell grabs of this character have been facedwith a problem where one or several of the shells of the grab encountersa relatively immovable object such as a large or rigidly fixed rock, forexample, in the removal of earth. This problem is increased when therock is larger than the grab. Such an encounter in previous devices hasprevented the closing of the shells and did not permit the lifting ofthe material, including the rock that was causing the trouble. Toovercome the problem it has previously been proposed to provide separateshells which are capable of independent movement, together with separatesystems of cables and rollers for operating the individual shells. Thisarrangement has proved disadvantageous because of the great number ofrollers, cables and parts required, which made the device cumbersome andsubject to numerous failures.

It has also heretofore been proposed to provide devices of thischaracter having link bars between the shell and the head member, saidlink bars being telescopic and having springs mounted inside them. Suchlink bars give and permit the shell to sink or move into the material,but since grabs are usually roughly handled and dropped onto thematerial to be picked up with a wide swing of the supporting boom andcable, it often happens that the link bars strike the material (such asscrap iron and the like), damaging the telescopic guides on the linkbars. In another proposed device, the shells have been provided withslots permitting limited yielding movement of any individual shellrelative to the others if, when closing, it should strike an immovableobject. Such slots, however, have a tendency to become clogged with thematerial that is being handled and this clogging hinders the properfunctioning of the grab.

It is accordingly an object of this invention to overcome thedisadvantages just referred to.

It is another object of this invention to provide an improved,non-clogging means for permitting independent movement of each grabshell for allowing a shell to lag behind the other shells uponencountering a strong resistance.

Another object of this invention is to provide means for cushioning theshock to which parts of the mechanism are subjected when a shellencounters a rigid object.

It is another object .to provide an improved means for allowing limitedlateral movement of the shell at an angle to the plane of its swingingmovement.

It is a further object of this invention to provide a multiple shellgrab of the type just referred to wherein the shells are pivotallyconnected to link bars and where- .in the pivotal connections areguarded and protected against blows, clogging and other damage. Anotherob-' cry of the head member.

ject is to provide a grab of this type having a head member of strongconstruction and yet of light weight so that a maximum pay load can behandled.

Still another object is to provide a multiple shell grab having shellsthat are operated frequently and that strike the material to be handledwith considerable force and yet do not subject the grab to excessiveimpact forces. It is another object to provide a device of this typehaving a strong link bar connection between the shells and the mechanismoperating the shells.

Other objects and advantages of the invention will further becomeapparent hereinafter and in the drawings in which:

Fig. 1 represents a top plan view of a multiple shell grab embodyingfeatures of this invention;

Fig. 2 represents a vertical sectional view of the grab shown in Fig. 1taken as indicated by the lines and arrows II-II which apear in Fig. 1,with certain parts being broken away and shown in section in order toillustrate important details;

Fig. 3 represents a sectional view taken as indicated by the lines andarrows IIII'II which appear in Fig. 2;

Fig. 4 represents a view in fractional elevation of one of the link barsthat connects one of the shells to the head member;

Figs. 5 and 6 represent sectional views taken as indicated by the linesand arrows VV and VI-VI which appear in Fig. 2;

Fig. 7 represents a perspective view of a modified form of one of thelink bars;

Fig. 8 represents a view in fractional elevation showing the modifiedlink bar of Fig. 7 connected to the head member;

Fig. 9 represents a view in section taken as indicated by the lines andarrows IX-lX which appear in Fig. 8;

Figs. 10 and 11 represent modified forms of the apertures of the ears ofthe head member; and

Fig. 12 represents a fractional view of One of the head member ears witha resilient cushion disposed therein.

Although specific terms are used in the following description forclarity, these terms are intended to refer only to the structure shownin the drawings and are not intended to limit the scope of theinvention.

Turning now to the specific form of the invention selected forillustration in the drawings, the number 20 designates a grab head whichis hell shaped and which is suspended from above by a rope or cable 21.Cable 21 is suspended from the boom of a crane or from similar apparatus(not shown) which operates to raise and lower, and otherwise positionthe grab. Suspended from head 20 by means of another rope or cable 22 isa base 23, which is of circular shape and which has pivotally mountedabout its periphery in star fashion a plurality of grab claws or shells24. A plurality of rigid link bars 25 are pivotally connected betweenthe shells 24 and head member 20 at equally spaced points around theperiph- The upper ends of link bars 25 are slidably pivoted to outwardlyextending ears 26 which are aifixed to the outer periphery of headmember 20. Cable 22 is trained around a series of pulleys 27 carried onhead member 20, and another series of pulleys 28 carried on the base 23,which allow the base to be raised and lowered relative to the headmember. When power is applied to cable 22 to pull it in an upwarddirection, the base 23 is raised toward the head 20 and the link bars 25coact with the base and head to swing the shells 24 about their pivotedconnection with the base to their closed position. When cable 22 isreleased from tension, the weight of the base 23 together with theweight of the shells 24 and the link bars 25 is -suflicient to swingopen the shells 24 by gravity action The head member 20 is bell or domeshaped, having a peripheral flange 31. Welded to the side walls 32 ofhead 20 are a number of ears 26 each of which has an aperture 33 formedtherein in which is positioned a barrel shaped transverse shaft 34 (Pig;A pin 35, having a slotted head 36 and a threaded end 37 on which isturned a nut 38, is centrally located within shaft 34 and serves toconnect aperture 33 with the hollow arms 41, 42 of link bar 25. Aperture33 is sufficiently large by comparison with shaft 34 to provideclearance that permits the longitudinal axis of the sleeve to rockwithin the aperture. Ears 26 are provided with sidewalls 43 that areangled at 44. A resilient pad 39 is aflixed in the upper extremity ofthe inner wall of aperture 33 of each ear 26 (Fig. 12). Figs. and 11show modifications in the shape of the ear apertures, a substantiallyoval shaped aperture 33a and a kidney shaped aperture 33b. Immediatelybelow ears 26, resilient pads 40 are securely but removably attached towall 32.

Each link bar 25 includes a hollow substantially square shaped middleportion 45 and an upper fork section 46, as well as a lower fork section47 formed by the arms 48, 49. The arms of the lower fork section 47 arereinforced by a plate 50 (Figs. 2 and 7), which is welded or otherwisesecured to the section 47 at the juncture of the arms 48, 49. Plate 50is of trapezoidal configuration and has a web 51 which extendsdiagonally from one side of the bar 25 to the other, within the forkformed by the arms 48, 49. Reinforcement straps 54 are welded betweenthe upper arms 41, 42 and lower arms 48, 49. Inner holes 56 are providedin the arms to admit the pins, and holes 57 are provided in the outersurfaces of the arms for allowing the admission of a screw driver orother tool to rotate the pin into its tightened position. The modifiedlink bar 25a shown in Fig. 7 is provided with slots 58 which coact withthe circular holes 61 provided in the car 26 illustrated in Fig. 9, forallowing longitudinal n ovement of link bar 25a with respect to headmember 2 It will be noted that the arms of the link bars 25 and 25a aresubstantially channel shaped and have plates 60 welded to the edges ofthe flanges of the arms to form a strong, rigid structure.

The base 23 comprises a circular upper plate 62 and a circular lowerplate 63 having radial slots 64 formed therein to permit swinging ofshells 24. Upper and lower plates 62 and 63 are rigidly joined to eachother by vertical webs 65 which are arranged in pairs at equally spacedpoints around the peripheral edge of the base at the edges of slots 64.The shells 24 are pivotally connected to the base member 23 between thewebs 65 which have holes 66 that receive barrel shaped pivot shafts 67on which a shell is hung.

Each grab shell 24 is formed of a curved metal plate 68, to the convexface of which is welded or otherwise secured a central perpendicularsaddle plate 71 having side plates 72 affixed to the curved plate 68.The end of saddle plate 71 is formed into a stop flange 73 that isarranged to coact with stop lugs 74 mounted on upper plate 62 of basemember 23, to limit the upward swing of shells 24. A resilient pad 75 isremovably attached to flange 73 to cushion the shock of contact betweenflange 73 and lugs 74.

The central upper portion of eachsaddle plate 71 is apertured at 76(Fig. 6), and a barrel shaped, transverse pivot shaft 77 extends throughaperture 76 to pivot the shell 24 to link bar 25. Both pivot shaft 67connecting shell 24 with base member 23, and pivot shaft 77 connectingshell 24 with link bar 25 are loosely connected within their associatedapertures to provide sufficient clearance to allow limited lateralmovement of the connected parts, permitting shell 24 to rock laterallywith respect to the plane of the shells swinging movement. Reinforcingplates 78 are welded to saddle plate 71 adjacent t e aperture 76.

In operation the grab is suspended on cable 21 with cable 22 relaxed andthe shells 24 open as in Fig. 2. The grab is lowered on top of thematerial to be lifted as shown in Fig. 2, and the cable 22 is pulled toclose the grab shells 24. The pulling on cable 22 causes base member 23and head member 20 to move toward each other. This relative movement ofthe head and base members acts upon link bars 25 to force the shells 24to rotate upon their pivot shaft 67. Upon encountering resistance eachshell 24 is allowed, by the loose pivot connections at shafts 67, 77 and34 and by the barrel shape of the pivot shafts, to rock independently ofeach other and to follow the line of least resistance in scooping up thematerial to be excavated or handled. In closing grab shells 24, pads 40cushion the shock and also prevent rocking of the closed shells. Shouldone or several of the shells 24 encounter a resisting force that impedesits progress, the slotted arrangement of the cars 26 as typified in Fig.2, or the slotted arrangement 58 of the upper fork 46 as shown in Figs.'7 and 8, allow such a shell to lag behind the others in closing. Itwill be noted that the outer surface of arms 41, 42, 48, 49 protect thepivot mechanism from blows, damage and from clogging, and thatreinforcing straps 54 and reinforcing plate 50 provide added strength toreinforce link bars 25. Straps 54 and plate 50 are positioned tominimize clogging and the pouring of material through the space betweenthe forked arms. After the shells 24 have closed the grab is lifted bymeans of cable 21 and swung to position for emptying, whereupon thetension on cable 22 is released and the weight of the load plus theweight of the base member 23, shells 24, and link bars 25 act to movebase member 23 away fro-m head member 20 and open shells 24 to releasethe load.

On opening the shells 24, resilient pad 75 on stop flange 73 of saddleplate 71 contacts lug 74 of base member 23 to cushion the strain ofimpact.

The bell or dome shape of the head member 20 is of particular advantagesince it combines great strength with light weight and with the headmember of light weight the pay load is proportionately increased. Thelocation adjacent the head member of the slots that allow a shell to lagbehind the others has several advantages, the slots are less likely tobecome clogged or receive blows and the weight of the link bars and theshells are added to the weight of the base to aid in moving the baseaway from the head to open the shells. The pivot connections include abarrel shaped shaft positioned within apertures of sutiicient clearancefor allowing a rocking action to permit the shells to follow the line ofleast resistance in their downward swing, and the hollow double forkedarms protect the pivot components against blows while the resilient padscushion the stop limits of the mechanism.

It is to be understood that the form of the invention herein shown anddescribed is to be taken as a preferred embodiment. Various changes maybe made in the shape, size and arrangement of parts. Equivalent elementsmay be substituted for those described herein, parts may be reversed,and certain features of the invention may be utilized independently ofthe use of other features, all without departing from the spirit of theinvention or the scope of the subjoined claims.

Having thus described my invention, I claim:

1. A multiple shell grab comprising a head member, a base membernormally positioned below the head member, means connected to the headand base members for moving said head and base members toward each otheragainst the action of gravity, a plurality of grab shells pivotallyconnected to said base member in star fashion with capacity for swingingmovement to open and close said shells, substantially rigid meanspivotally connected to said head member and pivotally connected to saidshells for swinging said shells in response to the movement-between saidhead and base members, and connecting means including a lost motionconnection adjacent to said head member between said rigid means andsaid head member providing for movement of said rigid means in adirection generally extending between said head and base members toprovide for a shell lagging behind the other shells in closing uponencountering a strong resistance.

-2. The multiple shell grab defined in claim 1, wherein said head memberis hell shaped.

3. The multiple shell grab defined in claim 1, wherein resilient stopmeans are interposed between said base l member and the shells forlimiting the swinging movement of the shells.

4. The multiple shell grab defined in claim 3, wherein said stop meansincludes a resilient pad mounted on a flange of the shell near itspivotal connection to said base member, and a lug mounted on said basemember providing for engagement with said resilient pad when said shellsare opened.

5. The multiple shell grab defined in claim 1, wherein saidsubstantially rigid means includes a rigid bar with a pair of armsforming a forked upper end, and said lost motion connection includes aslot formed in the arms of said bar.

6. The multiple shell grab defined in claim 1, wherein said lost motionconnection includes an ear rigidly affixed to said head member, said earhaving an elongated aperture formed therein, said substantially rigidmeans being connected into said aperture.

7. The multiple shell grab defined in claim 6, wherein said aperture iskidney shaped.

8. The multiple shell grab defined in claim 6, wherein said aperture issubstantially oval shaped.

9. The multiple shell grab defined in claim 6, said aperture havingresilient means afiixed at the extremity of its inner wall forcushioning shock.

10. The multiple shell grab defined in claim 6, wherein the side wallsof said ears are angled.

11. The multiple shell grab defined in claim 6, wherein resilient stopmeans are aflixed inside the elongated aperture of said ear.

12. A multiple shell grab comprising a head member, a base membernormally positioned below the head member, means connected to the headand base member for moving said head and base member toward each otheragainst the action of gravity, a plurality of grab shells pivotallyconnected to said base member in star fashion with capacity for swingingmovement to open and close said shells, shell moving means including asubstantially rigid link bar for moving said shells in response to themovement between said head and base members, and connecting meansincluding a lost motion connection adjacent to said head member betweensaid link bar and said head member providing for movement of said linkbar in a direction generally extending between said head and basemembers to provide for a shell lagging behind the other shells inclosing upon encountering a strong resistance, said shell moving meansincluding a rigid link bar having a substantially square shaped middleportion and arms forming upper and lower forked end portions, a barrelshaped transverse shaft extending between the arms of said forked endportions, said shaft of the upper forked end portion being looselypivotally connected to said connecting means, and said shaft of thelower forked end portion being loosely pivotally connected to one ofsaid shells whereby said shells have capacity for limited lateralmovement at an angle to the plane of their swinging movement.

13. The multiple shell grab defined in claim 12, wherein said arms arehollow and the ends of the transverse shaft extending between said armsare recessed within the interior of said arms whereby to protect saidshaft ends against blows and damage.

14. The multiple shell grab defined in claim 12, where ally divergingportion of said arms that form said lower forked end portion.

15. The multiple shell grab comprising a head member, a base membernormally positioned below the head member, pulley means connected tosaid head and base members and a system of cables trained around saidpulley means for moving said head and base members toward each'otheragainst theaction of gravity, a plurality of grab shells pivotallyconnected to said base member instar fashion with capacity for swingingmovement to open and close said shells, substantially rigid meanspivotally connected to said head member and pivotally connected to saidshells for swinging said shells in response to the movement between saidhead and base members, and connecting means including a lost motionconnection adjacent to said head member between said rigid means andsaid head member providing for movement of said rigid means in adirection generally extending between said head'and base members toprovide a shell lagging behind the other shells in closing uponencountering a strong resistance, and means connected to said rigidmeans, to said connecting means and to said shells providing for limitedlateral movement of said shells at an angle to the plane of theirswinging movement.

References Cited in the file of this patent UNITED STATES PATENTS254,824 'Johnson Mar. 14, 1882 271,538 Stone Jan. 30, 1883 1,935,898Zimmerman et a1. Nov. 21, 1933 FOREIGN PATENTS 347,093 Germany Jan. 12,1922 466,546 Germany Oct. 9, 1928 515,809 Great Britain Dec. 14, 1939456,384 Italy Apr. 1, 1950

